X-ray imaging is applied in various technical fields in order to obtain information about internal structures within a region of interest of an object. For example, medical X-ray imaging devices are used to obtain information about internal structures within a patient's body.
Basically, an X-ray imaging device comprises at least an X-ray source and an X-ray detector arranged at opposite sides of an observation volume in which the region of interest is to be placed.
In a stationary approach, both the X-ray source and the X-ray detector are arranged at fixed locations and X-rays coming from the X-ray source are transmitted through the region of interest in the observation volume and are partly attenuated therein and are then detected by the X-ray detector. In such approach, the X-ray detector is typically a two-dimensional X-ray detector having multiple detector elements arranged in a two-dimensional matrix. In such approach, a field of view is generally determined by the size of the two-dimensional X-ray detector.
In an alternative approach, at least one of the X-ray source and the X-ray detector is not stationary but is moved during an image acquisition procedure. In such approach, the X-ray detector is typically substantially smaller than the cross-section of the region of interest such that an image of the entire region of interest may not be acquired for all sub-regions of the region of interest simultaneously. Accordingly, in such dynamic approach, an entire image is acquired by successively scanning the X-ray beam and/or the X-ray detector along the region of interest. Image information is acquired for each of the sub-regions of the region of interest successively and the entire image may be derived by combining the image information of all sub-regions. For example, an X-ray line detector comprising multiple X-ray detector elements arranged as a one-dimensional matrix, i.e. arranged along a line, may be used for acquiring an entire image of a region of interest by scanning the line detector in a direction perpendicular to the line direction of the detector.
In a further improved embodiment of such scanning approach, the X-ray detector does not only comprise a single X-ray line detector but comprises a plurality of X-ray line detectors arranged one behind the other with respect to the scanning direction. In such approach, most of the sub-regions of the region of interest are not only scanned by a single X-ray line detector but during the image acquisition procedure, image information for this sub-region is acquired successively by a multiplicity of X-ray line detectors.
For example, WO 2007/050025 A2 discloses a method and arrangement relating to X-ray imaging in which an X-ray apparatus comprises an X-ray source for generating X-rays emerging from a focal spot, a multi-slit collimator, a line detector assembly and an exposure volume arranged between the collimator and the detector assembly. The line detector assembly comprises multiple lines of X-ray detector elements. The X-ray source, the collimator and the detector assembly are arranged in series so that each detector line is aligned with a corresponding collimator slit and simultaneously displaceable by a scan motion relative that exposure volume.
However, it has been observed that with conventional approaches of scanning X-ray imaging, there is a risk of excessive X-ray dose exposure at least when acquiring image information for some of the sub-regions within the region of interest. Such problem of X-ray overexposure may occur specifically in applications with only short scanning distances or angles. Furthermore, there may be a risk of motion blur due to patient movement during X-ray image acquisition.